1. Field of the Invention
The invention generally relates to electronics, and in particular, to a data communications receiver in which an analog-to-digital converter is present.
2. Description of the Related Art
Reducing power dissipation is important in nearly all data communication products, but it is especially important in a battery-powered wireless transceiver for the extension of operating time.
The radio frequency (RF) and analog portion of a wireless transceiver, typically referred to as the “radio,” can be divided into a receiver (Rx) and a transmitter (Tx). The power dissipation of a typical receiver is shown in FIG. 1. As illustrated in FIG. 1, the analog-to-digital converter (ADC) is responsible for a relatively large amount of the receiver's power consumption. In the illustrated example, the ADC consumes about 27%. The local oscillator (LO) consumes about 24%, the analog baseband (aBB) consumes about 16%, the digital intermediate frequency (D I/F) consumes about 12%, the low noise amplifier (LNA) consumes about 9%, and other circuits consume about 12%.
Co-existence of wireless communication links from different wireless standards, and a generally crowded wireless spectrum results in “interfering” radio signals near the frequency of a desired radio signal to be received, as illustrated in FIG. 9.
In an extreme case, the presence of a relatively large interferer near the desired signal makes reception of the desired signal impossible. Even in a relatively good case, the ability to handle a relatively large interferer increases the linearity and baseband filtering requirements of the radio, which in turn increases the radio's cost and power.
One conventional solution to the problem of a large interferer is to increase the linearity and increase the analog baseband requirements of the radio front end. This approach increases both the cost and the power used by the radio.
In another approach illustrated in FIG. 10, the interfering signal is separated at baseband, then up-converted to RF and subtracted from the total RF signal. See Aminghasem Safarian, et al., Integrated Blocker Filtering RF Front Ends, Radio Frequency Integrated Circuits (RFIC) Symposium, Jun. 3-5, 2007, 2007 Institute of Electrical and Electronics Engineers (IEEE), pp. 13-16.